Treatment of menthadiene-7-carbinols and product thereof



Patented on. 7, 1947 attests TREATMENT OF MENTHADlENE-l-CAR- BINOLS AND PRODUCT THEREOF Joseph P. Bali: and Albert 1!. But, Jacksonville, Flm, asairnorl, by memo assignments, to The Gliddcn Company, Cleveland, Ohio, 1 corporation of Ohio- NoDa-awine. Appllcetion March it, 19%,

serial No. 527,133.

t @laime. (i. see-ens) l p 2 The present invention relotes to the prepare, tion of new alcohol compositions, to the alcohols E C OH H C CH resulting therefrom, and their esters and ethers. More particularly this invention is directed to B c CH of H C CH primary monccycllc alcohols containing eleven 55 s carbon atoms.

In c. s. Patent 2,340,294,,the formation or on i! alcohol by the reaction of nopinene (beta-pinene) CE with anhydrous formaldehyde is disclosed. The alcohol so produced possesses the empirical ioriii W mule. 01113130, and is s bicyclic primary unsaturated alcohol. Because oi its preparation from ncpinene, the alcohol has been named Nopol. 3 CHI It is believed to possess the following structure: l

1 V o-om-cmon CH no cm on g, HaC CH5 1 3 :C CE: m V

These alcohols may be generically characterized as menthodiene-,=7-cerbinols. The complexity of mixtures oi any or all oi the isomeric compounds 35 i readily apparent since the product of any established or'demonstrable mechanism for their preparation may be optically active or optically inactive depending upon the particular mechanism chosen. The degree, or even total absence, of optical activity of this particular product will thus be oi little import in general in the determination oi the composition of the mixture of alcohols comprising this product.

It is possible to convert ncpol into a number oi" isomeric monocyclic elcoho1s,of the some generic formula. CuHmO, apparently difiering from each other only in the position of the double bonds. That is to say, they have substantially the same relation to each other that the CioHm hydrocarbong dipentene, terpinene, terpinolene and phellandrene, for example, bear to each other. til

These alcohols, obtained either as the principal product,-or as by-products of reactions involving acid catalysis, liquid phase pyrolysis, or vapor phase pyrolysis of nopol, have boiling points All, of the alcohols whose constitutions have in the range of from substantially 125 C. t been given possess two double bonds, hence are Stantialll at a Pressure of 10 unsaturated. Together with this undesirable as referred a 760 barometer and characteristic, or as a result of it, these alcohols snow considerable variation in their physical propare readily oxidized. The instability oi the menerties. Representatives of the e alcohols ma thadienel-carbinols is sufficiently great to aii'ect consist of such monocyclic CuHiaO alcohols as: 40 adversely the range or applications in industry c cH, cn,oH c-cg,-ca,og in which they ,might otherwise be employed. me on no CH, It is accordingly, an object of our invention to reduce the degree 01' unsaturation in the monocyclic isomers of compounds oi the class con- CH sisting of nopols, and ethers and esters thereof.

3 It is another object or our invention to produce the saturated alcohols by hydrogenation of mo CH me on. menthadiene-i-carbinols.

fill mgnthadienc 'l-carbinols to a disproportiona- Another object or our invention is to subject I amazes tion mechanism to reduce the degree of unsaturation.

Another object of our invention is to produce mixtures of the reaction product obtained by hydrogenation of menthadiene-T-carbinols and the disproportionation product of the hydrogenation reaction product.

Still another object of our invention is to heat the menthadiene-l-carbinols in the -presence of a hydrogenation catalyst to reduce the degree of unsaturation.

It is yet another object to produce 4-isopropylcyclohexyi-ethanol from menthadiene-l-carbinols.

It is another object of our invention to produce para-isopropyl-phenethanol from menthadiene- 'l-carbinols.

Other objects and a fuller understanding of our invention will be had by referring to the following description and claims.

when the hiehthadiehe-l-carbihols are subiected to hydrogenation, saturation is readily attained with the formation of 4-isopropyl-cyclohexyl ethanol. The reaction is usually carried out under pressure and in the presence of one of the catalysts usuall employed for hydrogenation.

The equivalent reactions proceed equally well with the esters or others of the isomeric monocyclic alcohols, whether produced by esteriilcation or etherlfication of these monocyclic alcohols or if they result from the formation of the esters or ethers of nopol before the subjection of the bicyclic compound to acid catalysis or to pyrolysis to form the corresponding monocyclic compounds.

When disproportlonation is initiated in the case oi the monocyclic alcohols, it has been found to result in the formation of 4-isopropylcyclohexyl-ethanol and the aromatic alcohol para-lsopropyl-phenethanol.

Our invention is additionally exemplified by consideration of the specific examples given below:

Example I Seventy-one parts of a mixture oi the isomeric monocyclic alcohols resulting from liquid phase pyrolysis of nopol, this mixture having a boiling point of substantially 127 C. at mm. pressure, index of refraction at 25 C. (N) of substantially 1.49, and a specific rotation at 25 0. (4rd) of substantially +3 (using a 10 cm. polarimeter tube) were taken, and hydrogenated, using a nickel catalyst, at a temperature of 175 C, and pressure of about 4000 pounds per square inch.

After separation from the reaction mass by fractional distillation, fifty parts of the desired product, 4-isopropyl-cyclohexyl-ethanol were obtained. This product was found to possess the following characteristics:

Boiling point (10 mm. pressure) C 1265-1275 Six hundred parts of a mixture of the isomeric monocyclic alcohols resulting from fractionation of vapor phase pyrolyzed nopol were taken, having the following properties:

Boiling point at 10 mm C 123.5-125 Refractive index at 25 0.................. Ca 1.497

The mixture was heated with ten parts of palladium on charcoal at temperatures between 175 .4 C. and 230 C. until the bromine absorption value of the reaction mass became substantially zero. Heating was discontinued, and the mass filtered to recover the liquid product, which was then fractionated. The fore-run consisting almost entirely of hydrocarbons, amounted to about 150 parts. The principal cut, consisting of thedieproportionated product distilled in a temperature range of from 121 C. to 128 C., the fractionation being conducted at a pressure of 10 mm. of mer- Because of the comparatively narrow temperature range for fractionation, quantitative separation of the reaction products could not readily be achieved. It was found, however, that the highest boiling fractions, that is fractions collected at temperatures Just below the maximum value of 128 C. consisted of practically pure para-isopropyl-phenethanol, with a refractive index at 25 C. of 1.515 and a density at 25C. of .9605. Proof of constitution was afforded, firstly, by conversion of the alcohol to terephthalic acid, and secondly, by conversion to the naphthyluretane, which had a melting point of 99-i00 0., a value identical with the melting point of naphthylvuret'ane, freshly prepared from para-isopropylphenethanol, which in turn had been synthesized by reduction of the butyl ester of cymene-7-carboxylic acid.

Example III Nopol was heated in the liquid phase under pressure for five hours at temperatures in the range of from 250 to 290 C. At the end of this period. the reaction product was fractionated, and the fraction collected in the temperature range of from substantially to 129 C. at 10 mm, pressure, and the mixture of menthadiene-7-carbinols thus obtained had a refractive index at 25 C. of 1.50, and a specific rotation at 25 C. (0nd) of +2.5 (using a 10 cm. polarimeter tube). This mixture was then heated over palladium, the temperature being held within the range of from to C. The reaction product had a boiling point of l24-126 at 10 mm. pressure, was found to be composed of a mixture of para-isopropyl-phenethanol and 4-isopropylcyclohexyl-ethanol, and was a colorless oil of pleasant odor.

Ethers and esters of the alcohols of the present invention may, of course, be prepared by etheriflcation or esterification of the alcohols, or may be prepared by the hydrogenation or, disproportionation of the corresponding others and esters menthadiene-7-carbinois.

In the process of formation of the disproportionation products, it is believed that the mechanism of the reaction may be represented by the following type equation:

HiC o EC CH: CE 3 8 0/ --e Hg 0 C H B H:G CH: Menthol-lione- E 7-corbinol H N opol HiC OH| C-CHr-CHaOH CH-CHr-CHaOH 2H0 CH HsC CH2 .ethanol in various proportions.

. While this equation shows the reaction product to consist of a mixture of two moles of paraisopropyl-phenethanol with one mole oi 4-isopropyl-cyclohexyl-ethanol, it will be understood that the progress; of the reaction may becontrolled to give final products consisting of admixtures'of the isomers oil nopol with para-iso-- propyl-phenethanol and i-isopropyl-cyclohexyl These and othervariationsto be employed catalyst to reduce'the degree of will be apparent to those skilled in the art. For

example, the menthadiene-l-carbiriols may first" be partiallyhydrogenated and the resulting mixture of partially hydrogenated alcohols subsequently exposed to-.the disproportionation re-- action. a

Again, we have disclosed the utilization of nickel catalysts for hydrogenation, and otppallaa I dium catalystsdor disproportionation, but it will be evident that the other catalysts which are 1 known to activate these types-oi reactions may be used without substantially afiectingthe natures or fields of the processes disclosed, or of the compositions resulting from the processes employed' Although we have described our invention with a certain degree of particularity, it is understood that the present disclosure is only by way of disa closure and that numerous changes may be made in the operations of-the process and in specific composition without departing from the spirit and scope of our invention. What we claim is:

a 6 1. The process which comprises catalytically disproportionating the monocyclic isomers 01 7 'methylol A pinene.

2."As anew composition of matter, t-iso- ;propyl-cyclohexy1-ethano1.- 4

3. The process which consists in .heatinga menthadiene-7-carbinol' with a hydrogenation the carbinol. w h a JOSEPH P.-BAIN.

ALB RT H. BEST."

REFERENCES- orrEn The following references are of record in the file of this patent: i

UNITED STATEB PATENTS OTHER REFERENCES lBraun, Ber. Deut. Chem., son, p; 102-10 927).

'Becherer, "Helv. Chim. Acta. vol. 8, pp. 184- (1925).

unsaturatio'n oi 

